IPPM T. Mizrahi
Internet-Draft Huawei
Intended status: Standards Track F. Brockners
Expires: August 21, 2021 Cisco
S. Bhandari, Ed.
Thoughtspot
R. Sivakolundu
C. Pignataro
Cisco
A. Kfir
B. Gafni
Nvidia
M. Spiegel
Barefoot Networks
J. Lemon
Broadcom
February 17, 2021
In-situ OAM Flags
draft-ietf-ippm-ioam-flags-04
Abstract
In-situ Operations, Administration, and Maintenance (IOAM) records
operational and telemetry information in the packet while the packet
traverses a path between two points in the network. This document
presents new flags in the IOAM Trace Option headers. Specifically,
the document defines the Loopback and Active flags.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 21, 2021.
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Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
3. New IOAM Trace Option Flags . . . . . . . . . . . . . . . . . 3
4. Loopback in IOAM . . . . . . . . . . . . . . . . . . . . . . 3
5. Active Measurement with IOAM . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Performance Considerations . . . . . . . . . . . . . . . . . 7
8. Security Considerations . . . . . . . . . . . . . . . . . . . 7
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
IOAM [I-D.ietf-ippm-ioam-data] is used for monitoring traffic in the
network by incorporating IOAM data fields into in-flight data
packets.
IOAM data may be represented in one of four possible IOAM options:
Pre-allocated Trace Option, Incremental Trace Option, Proof of
Transit (POT) Option, and Edge-to-Edge Option. This document defines
two new flags in the Pre-allocated and Incremental Trace options: the
Loopback and Active flags.
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2. Conventions
2.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2.2. Terminology
Abbreviations used in this document:
IOAM: In-situ Operations, Administration, and Maintenance
OAM: Operations, Administration, and Maintenance
3. New IOAM Trace Option Flags
This document defines two new flags in the Pre-allocated and
Incremental Trace options:
Bit 1 "Loopback" (L-bit). Loopback mode is used to send a copy of a
packet back towards the source, as further described in Section 4.
Bit 2 "Active" (A-bit). When set, this indicates that this is an
active IOAM packet, where "active" is used in the sense defined in
[RFC7799], rather than a data packet. The packet may be an IOAM
probe packet, or a replicated data packet (the second and third
use cases of Section 5).
4. Loopback in IOAM
Loopback is used for triggering each transit device along the path to
loop back a copy of the data packet. Loopback allows an IOAM
encapsulating node to trace the path to a given destination, and to
receive per-hop data about both the forward and the return path.
Loopback is intended to provide an accelerated alternative to
Traceroute, that allows the encapsulating node to receive responses
from multiple transit nodes along the path in less then one round-
trip-time, and by sending a single packet.
Loopback can be used only if a return path from transit nodes and
destination nodes towards the source (encapsulating node) exists.
Specifically, loopback is only applicable in encapsulations in which
the identity of the encapsulating node is available in the
encapsulation header. If an encapsulating node receives a looped
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back packet that was not originated from the current encapsulating
node, the packet is dropped.
The encapsulating node either generates synthetic packets with an
IOAM trace option that has the loopback flag set, or sets the loopack
flag in a subset of the in-transit data packets. Loopback is used
either proactively or on-demand, i.e., when a failure is detected.
The encapsulating node also needs to ensure that sufficient space is
available in the IOAM header for loopback operation, which includes
transit nodes adding trace data on the original path and then again
on the return path.
An IOAM trace option that has the loopback bit set MUST have the
value '1' in the most significant bit of IOAM-Trace-Type, and '0' in
the rest of the bits of IOAM-Trace-Type. Thus, every transit node
that processes this trace option only adds a single data field, which
is the Hop_Lim and node_id data field. The reason for allowing a
single data field per hop is to minimize the impact of amplification
attacks.
A loopback bit that is set indicates to the transit nodes processing
this option that they are to create a copy of the received packet and
send the copy back to the source of the packet. In this context the
source is the IOAM encapsulating node, and it is assumed that the
source address is available in the encapsulation header. Thus, the
source address of the original packet is used as the destination
address in the copied packet. The address of the node performing the
copy operation is used as the source address. The IOAM transit node
pushes the required data field *after* creating the copy of the
packet, in order to allow any egress-dependent information to be set
based on the egress of the copy rather than the original packet. The
copy is also truncated, i.e., any payload that resides after the IOAM
option(s) is removed before transmitting the looped back packet back
towards the encapsulating node. The original packet continues
towards its destination. The L-bit MUST be cleared in the copy of
the packet that a node sends back towards the source.
On its way back towards the source, the copied packet is processed
like any other packet with IOAM information, including adding any
requested data at each transit node (assuming there is sufficient
space).
Once the return packet reaches the IOAM domain boundary, IOAM
decapsulation occurs as with any other packet containing IOAM
information. Note that the looped back packet does not have the
L-bit set. The IOAM encapsulating node that initiated the original
loopback packet recognizes a received packet as an IOAM looped-back
packet by checking the Node ID in the Hop_Lim/node_id field that
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corresponds to the first hop. If the Node ID matches the current
IOAM node, it indicates that this is a looped back packet that was
initiated by the current IOAM node, and processed accordingly. If
there is no match in the Node ID, the packet is processed like a
conventional IOAM-encapsulated packet.
Note that an IOAM encapsulating node may either be an endpoint (such
as an IPv6 host), or a switch/router that pushes a tunnel
encapsulation onto data packets. In both cases, the functionality
that was described above avoids IOAM data leaks from the IOAM domain.
Specificallly, if an IOAM looped-back packet reaches an IOAM boundary
node that is not the IOAM node that initiated the loopback, the node
does not process the packet as a loopback; the IOAM encapsulation is
removed, and since the packet does not have any payload it is
terminated. In either case, when the packet reaches the IOAM
boundary its IOAM encapsulation is removed, preventing IOAM
information from leaking out from the IOAM domain.
5. Active Measurement with IOAM
Active measurement methods [RFC7799] make use of synthetically
generated packets in order to facilitate the measurement. This
section presents use cases of active measurement using the IOAM
Active flag.
The active flag indicates that a packet is used for active
measurement. An IOAM decapsulating node that receives a packet with
the Active flag set in one of its Trace options must terminate the
packet. The active flag is intended to simplify the implementation
of decapsulating nodes by indicating that the packet should not be
forwarded further. It is not intended as a replacement for existing
active OAM protocols, which may run in higher layers and make use of
the active flag.
An example of an IOAM deployment scenario is illustrated in Figure 1.
The figure depicts two endpoints, a source and a destination. The
data traffic from the source to the destination is forwarded through
a set of network devices, including an IOAM encapsulating node, which
incorporates one or more IOAM options, a decapsulating node, which
removes the IOAM options, optionally one or more transit nodes. The
IOAM options are encapsulated in one of the IOAM encapsulation types,
e.g., [I-D.ietf-sfc-ioam-nsh], or [I-D.ietf-ippm-ioam-ipv6-options].
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+--------+ +--------+ +--------+ +--------+ +--------+
| | | IOAM |.....| IOAM |.....| IOAM | | |
+--------+ +--------+ +--------+ +--------+ +--------+
| L2/L3 |<===>| L2/L3 |<===>| L2/L3 |<===>| L2/L3 |<===>| L2/L3 |
+--------+ +--------+ +--------+ +--------+ +--------+
Source Encapsulating Transit Decapsulating Destination
Node Node Node
<------------ IOAM domain ----------->
Figure 1: Network using IOAM.
This draft focuses on three possible use cases of active measurement
using IOAM. These use cases are described using the example of
Figure 1.
o Endpoint active measurement: synthetic probe packets are sent
between the source and destination, traversing the IOAM domain.
Since the probe packets are sent between the endpoints, these
packets are treated as data packets by the IOAM domain, and do not
require special treatment at the IOAM layer. Specifically, the
active flag is not used in this case, and the IOAM layer needs not
be aware that an active measurement mechanism is used at a higher
layer.
o IOAM active measurement using probe packets within the IOAM
domain: probe packets are generated and transmitted by the IOAM
encapsulating node, and are expected to be terminated by the
decapsulating node. IOAM data related to probe packets may be
exported by one or more nodes along its path, by an exporting
protocol that is outside the scope of this document (e.g.,
[I-D.spiegel-ippm-ioam-rawexport]). Probe packets include a Trace
Option which has its Active flag set, indicating that the
decapsulating node must terminate them.
o IOAM active measurement using replicated data packets: probe
packets are created by the encapsulating node by selecting some or
all of the en route data packets and replicating them. A selected
data packet that is replicated, and its (possibly truncated) copy
is forwarded with one or more IOAM option, while the original
packet is forwarded normally, without IOAM options. To the extent
possible, the original data packet and its replica are forwarded
through the same path. The replica includes a Trace Option that
has its Active flag set, indicating that the decapsulating node
should terminate it. It should be noted that the current document
defines the role of the active flag in allowing the decapsulating
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node to terminate the packet, but the replication functionality in
this context is outside the scope of this document.
6. IANA Considerations
IANA is requested to allocate the following bits in the "IOAM Trace
Flags Registry" as follows:
Bit 1 "Loopback" (L-bit)
Bit 2 "Active" (A-bit)
Note that bit 0 is the most significant bit in the Flags Registry.
7. Performance Considerations
Each of the flags that are defined in this document may have
performance implications. When using the loopback mechanism a copy
of the data packet is sent back to the sender, thus generating more
traffic than originally sent by the endpoints. Using active
measurement with the active flag requires the use of synthetic
(overhead) traffic.
Each of the mechanisms that use the flags above has a cost in terms
of the network bandwidth, and may potentially load the node that
analyzes the data. Therefore, it MUST be possible to use each of the
mechanisms on a subset of the data traffic; an encapsulating node
needs to be able to set the Loopback and Active flag selectively, in
a way that considers the effect on the network performance.
Similarly, transit and decapsulating nodes need to be able to
selectively loop back packets with the Loopback flag, and to
selectively export packets. Specifically, rate limiting can be
enabled so as to ensure that the mechanisms are used at a rate that
does not significantly affect the network bandwidth, and does not
overload the receiving entity (or the source node in the case of
loopback).
8. Security Considerations
The security considerations of IOAM in general are discussed in
[I-D.ietf-ippm-ioam-data]. Specifically, an attacker may try to use
the functionality that is defined in this document to attack the
network.
An attacker may attempt to overload network devices by injecting
synthetic packets that include an IOAM Trace Option with one or more
of the flags defined in this document. Similarly, an on-path
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attacker may maliciously set one or more of the flags of transit
packets.
o Loopback flag: an attacker that sets this flag, either in
synthetic packets or transit packet, can potentially cause an
amplification, since each device along the path creates a copy of
the data packet and sends it back to the source. The attacker can
potentially leverage the loopback flag for a Distributed Denial of
Service (DDoS) attack, as multiple devices send looped-back copies
of a packet to a single source.
o Active flag: the impact of synthetic packets with the active flag
is no worse than synthetic data packets in which the Active flag
is not set. By setting the active flag in en route packets an
attacker can prevent these packets from reaching their
destination, since the packet is terminated by the decapsulating
device; however, note that an on-path attacker may achieve the
same goal by changing the destination address of a packet.
Another potential threat is amplification; if an attacker causes
transit switches to replicate more packets than they are intended
to replicate, either by setting the Active flag or by sending
synthetic packets, then traffic is amplified, causing bandwidth
degredation. As mentioned in Section 5, the specification of the
replication mechanism is not within the scope of this document. A
specification that defines the replication functionality should
also address the security aspects of this mechanism.
Some of the security threats that were discussed in this document may
be worse in a wide area network in which there are nested IOAM
domains. For example, if there are two nested IOAM domains that use
loopback, then a looped-back copy in the outer IOAM domain may be
forwarded through another (inner) IOAM domain and may be subject to
loopback in that (inner) IOAM domain, causing the amplification to be
worse than in the conventional case.
In order to mitigate the attacks described above, as described in
Section 7 it should be possible for IOAM-enabled devices to
selectively apply the mechanisms that use the flags defined in this
document to a subset of the traffic, and to limit the performance of
synthetically generated packets to a configurable rate; specifically,
network devices should be able to limit the rate of: (i) looped-back
traffic (at transit nodes), (ii) replicated active packets (at
encapsulating nodes), (iii) packets that are exported to a collector
(from either encapsulating nodes or transit nodes), and (iv)
synthetically generated packets (at encapsulating nodes).
Furthermore, as defined in Section 4, transit nodes that process a
packet with the Loopback flag only add a single data field, and
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truncate any payload that follows the IOAM option(s), thus
significanly limiting the possible impact of an amplification attack.
IOAM is assumed to be deployed in a restricted administrative domain,
thus limiting the scope of the threats above and their affect. This
is a fundamental assumtion with respect to the security aspects of
IOAM, as further discussed in [I-D.ietf-ippm-ioam-data].
9. References
9.1. Normative References
[I-D.ietf-ippm-ioam-data]
Brockners, F., Bhandari, S., and T. Mizrahi, "Data Fields
for In-situ OAM", draft-ietf-ippm-ioam-data-11 (work in
progress), November 2020.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
9.2. Informative References
[I-D.ietf-ippm-ioam-ipv6-options]
Bhandari, S., Brockners, F., Pignataro, C., Gredler, H.,
Leddy, J., Youell, S., Mizrahi, T., Kfir, A., Gafni, B.,
Lapukhov, P., Spiegel, M., Krishnan, S., Asati, R., and M.
Smith, "In-situ OAM IPv6 Options", draft-ietf-ippm-ioam-
ipv6-options-04 (work in progress), November 2020.
[I-D.ietf-sfc-ioam-nsh]
Brockners, F. and S. Bhandari, "Network Service Header
(NSH) Encapsulation for In-situ OAM (IOAM) Data", draft-
ietf-sfc-ioam-nsh-05 (work in progress), December 2020.
[I-D.spiegel-ippm-ioam-rawexport]
Spiegel, M., Brockners, F., Bhandari, S., and R.
Sivakolundu, "In-situ OAM raw data export with IPFIX",
draft-spiegel-ippm-ioam-rawexport-04 (work in progress),
November 2020.
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[RFC7799] Morton, A., "Active and Passive Metrics and Methods (with
Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799,
May 2016, <https://www.rfc-editor.org/info/rfc7799>.
Authors' Addresses
Tal Mizrahi
Huawei
Israel
Email: tal.mizrahi.phd@gmail.com
Frank Brockners
Cisco Systems, Inc.
Hansaallee 249, 3rd Floor
DUESSELDORF, NORDRHEIN-WESTFALEN 40549
Germany
Email: fbrockne@cisco.com
Shwetha Bhandari (editor)
Thoughtspot
3rd Floor, Indiqube Orion, 24th Main Rd, Garden Layout, HSR Layout
Bangalore, KARNATAKA 560 102
India
Email: shwetha.bhandari@thoughtspot.com
Ramesh Sivakolundu
Cisco Systems, Inc.
170 West Tasman Dr.
SAN JOSE, CA 95134
U.S.A.
Email: sramesh@cisco.com
Carlos Pignataro
Cisco Systems, Inc.
7200-11 Kit Creek Road
Research Triangle Park, NC 27709
United States
Email: cpignata@cisco.com
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Aviv Kfir
Nvidia
Email: avivk@nvidia.com
Barak Gafni
Nvidia
350 Oakmead Parkway, Suite 100
Sunnyvale, CA 94085
U.S.A.
Email: gbarak@nvidia.com
Mickey Spiegel
Barefoot Networks
4750 Patrick Henry Drive
Santa Clara, CA 95054
US
Email: mspiegel@barefootnetworks.com
Jennifer Lemon
Broadcom
270 Innovation Drive
San Jose, CA 95134
US
Email: jennifer.lemon@broadcom.com
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